High energy costs and environmental concerns over the generation of pollution require more energy efficient mechanisms for heating and cooling interior spaces. Utilizing renewable energy resources and, in some cases, waste heat from any number of sources improves energy efficiency. Mechanisms that use energy must be easily adapted to a number of different energy sources without the need for expensive or customized adaptors.
The interior spaces that require heating and cooling are not limited to living and working environments, but also extend to spaces involved in transportation for humans and perishable commodities. The method of providing heating and cooling must be economical, efficient to manufacture, and inexpensive to maintain in order to be readily accessible for any number of applications in everyday life.
The standard Carnot reversible heat pump cycle, which uses an expansion valve for expanding the refrigerant fluid and a mechanical compressor for the compression of the refrigerant vapor, has been in use for a wide variety of applications. Essentially, in the cooling mode, such systems pass saturated liquid refrigerant through an expansion valve to lower the refrigerant's pressure, and therefore the saturation temperature of the refrigerant correspondingly falls, and the cooled refrigerant is then directed to an evaporator where heat is absorbed from the atmosphere, thereby cooling the environmental space (or some other medium where cooling is desired).
This cycle may be reversible, thus permitting the same system to operate as a heat pump. To provide heating of a space, energy is added to the system by a compressor and ambient air. Most of the prior art devices that accomplish this task are known to consume large amounts of energy (usually electrical energy), and are inefficient in both the cooling and heating modes.
For example, FIG. 1 depicts a conventional heat pump device. As illustrated, this conventional heat pump system requires a common compressor unit to be driven by direct electric motor energy input, or power transferred from a rotating shaft, as in a vehicle system.
The benefits of heat powered heat pump devices designed for use in the home or office are well known. An example of a conventional heat powered heat pump is disclosed in U.S. Pat. No. 4,918,937.
U.S. Patent No. 4,918,937 provides an air conditioning system for an automobile that uses both a mechanical compressor and a refrigerant pump to motivate refrigerant through the system. The '937 patent discloses an engine-driven mechanical compressor that compresses the vaporized refrigerant until the pressure of refrigerant flowing from the refrigerant pump through a heat exchanger and an ejector is high enough to sufficiently pressurize the vaporized refrigerant. Once the required pressure level is met, the mechanical compressor is disengaged and the refrigerant pump, heat exchanger and ejector motivate the refrigerant through the system. One drawback of the '937 patent is that the system requires a mechanical compressor to compress the vaporized refrigerant being sent to the heat exchanger.
The present invention provides a heat pump system that avoids some or all of the aforesaid shortcomings in the prior art.